Laminated piezoelectric transducers have been used for acoustic transduction, fluid pumping, and power generation using flexure. Examples of acoustic applications include piezoelectric microphones, speakers, and piezoelectric pickups for electrically amplified instruments. Piezoelectric sensors are also used with high frequency sound in ultrasonic transducers for medical imaging.
In an effort to improve the performance of piezoelectric transducers, researchers have explored the properties of a device consisting of a curved piezoelectric diaphragm. Such approaches use the curvature of the diaphragm to convert extensional strains into radial motions, rather than relying upon flexure. This vibration is often referred to as the uniform mode. For this mode, it has been found that the resonance frequency and displacement amplitude of the curved diaphragm is inversely proportional to the radius of curvature, thus allowing for a magnification of radial displacements that cause acoustic waves in the surrounding medium. The investigations have also shown that clamped boundaries and extensional stresses cause additional flexural vibrations. The first natural frequency of the flexural mode is lower than that for the uniform mode, making it potentially useful for some applications. Experimental measurements and numerical computations have shown that the magnitude of the flexural vibrations is on the same order as those of the uniform mode. However, the flexural mode does not vibrate in phase across the diaphragm surface, leading to poor acoustic coupling to the surrounding medium.